This project is a study of the mixed-function oxidase system responsible for the biosynthesis of estrogens from androgens. The participating enzymes will be identified and their activities characterized at several levels of biological organization. Particulate enzymes will be solubilized, fractionated, purified and characterized individually and as reconstituted interacting systems. Enzymes in their native membranous environment will be defined with respect to cofactor, substrate and inhibitor specificities. Aromatizing activity of microsomes will be compared to that of mitochondria and activity in other cell fractions will be investigated. Aromatizing activity of the rhesus ovary will be compared to that of the human placenta. These studies will establish whether multiple aromatizing systems exist. They will analyze the role of molecular and cellular organization in aromatization and they will identify agents and systems which influence and modulate the synthesis of estrogens by this enzyme system.